Apparatus and an associated method for facilitating communications in a radio communication system that provides for data communications at multiple data rates

ABSTRACT

Apparatus, and an associated method, for facilitating operation of a radio communication system that provides for multi rate data communications, such as a CDMA 2000 system that provides for 1×EV-DV communication services. A supplemental pilot, or control, signal generator embodied at a mobile station generates a supplemental pilot, or control, signal that is sent on a newly defined supplemental pilot, or control, channel. As the data rates of data communicated upon a reverse supplemental channel changes, corresponding changes are made to the power level of the reverse supplemental pilot, or control, signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending U.S. application Ser. No.13/357,209 filed on Jan. 24, 2012, which is a continuation of patentedU.S. application Ser. No. 12/646,465 filed on Dec. 23, 2009, issued asU.S. Pat. No. 8,130,695 on Mar. 6, 2012, which is a continuation ofpatented U.S. application Ser. No. 10/512,850 filed on Oct. 28, 2004,issued as U.S. Pat. No. 7,660,277 on Feb. 9, 2010, which is a nationalstage entry of International Application No. PCT/US03/17625, filed Jun.5, 2003, which claims priority to provisional U.S. Application No.60/386,819 filed on Jun. 7, 2002 and provisional U.S. Application No.60/386,906 filed on Jun. 7, 2002, the entire disclosures of which arehereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to a manner by which tofacilitate communications in a radio communication system that providesfor data communications at multiple data rates, such as a CDMA 2000cellular communication system that provides for 1×EV-DV datacommunication services. More particularly, the present invention relatesto apparatus, and an associated method, that provides a pilot, or othercontrol, signal, of levels related to the data rates at which the datais communicated. When the data rate at which data is communicated ischanged, the levels at which the pilot, or other control, signal isgenerated correspondingly changes.

Because the pilot, or other control, signal is of a level matched withthe data rate at which data is communicated, the need otherwise toselect a highest power level corresponding to a highest data rate, bestto ensure successful communication of the data, is obviated. Bypermitting operation at reduced power levels, lessened amounts of powerare consumed during communications, and improved system performance andcapacity are permitted.

BACKGROUND OF THE INVENTION

Communication systems are endemic in modern society. Communication ofdata pursuant to many varied types of communication services isregularly needed. A communication system is used by which to effectuatethe communication of the data. Due to advancements in communicationtechnologies, new types of communication systems are being developed.

A communication system includes at least a first communication stationand a second communication station interconnected by way of acommunication channel. Data is communicated by the first communicationstation, referred to as a sending station, to the second communicationstation, referred to as a receiving station, by way of the communicationchannel. Data that is to be communicated by the sending station isconverted, if needed, into a form to permit the data to be communicatedupon the communication channel. And, the receiving station detects thedata communicated upon the communication channel and recovers theinformational content thereof.

A radio communication system is a type of communication system. In aradio communication system, a radio channel, defined upon a radio airinterface, forms the communication channel interconnecting the sendingand receiving stations. Conventional wireline communication systems, incontrast, require the use of fixed, wireline connections extendingbetween the communications stations upon which to define thecommunication channel.

A radio communication system provides various advantages in contrast toa wireline counterpart. Initial installation and deployment costsassociated with a radio communication system are generally less than thecosts required to install and deploy a corresponding wirelinecommunication system. And, a radio communication system can beimplemented as a mobile communication system in which one or more of thecommunication stations operable therein is permitted mobility.

A cellular communication system is an exemplary type of mobile radiocommunication system. Cellular communication systems have been installedthroughout significant portion of the populated areas of the world andhave achieved wide levels of usage. A cellular radio communicationsystem is a multi-user communication system in which radiocommunications are provided with a plurality of mobile stations.Telephonic communication of voice and data is effectuable by way of themobile stations. Mobile stations are sometimes of sizes to permit theirconvenient carriage by users of the mobile stations.

A cellular radio communication system includes network infrastructurethat is installed throughout the geographical area that is encompassedby the communication system. Mobile stations operable in the cellularcommunication system communicate, by way of radio channels, with basestations that form parts of the network infrastructure of thecommunication system.

Base stations are fixed-site radio transceiver that transceive data withthe mobile stations. The base stations are installed at spaced-apartlocations throughout the geographical area encompassed by thecommunication system. Each of the base stations defines a cell, formedof a portion of the geographical area. A cellular communication systemis so-called because of the cells that together define the coverage areaof the communication system.

When a mobile station is positioned within a cell defined by a basestation, communications are generally effectuable with the base stationthat defines the cell. Due to the inherit mobility of a mobile station,the mobile station might travel between cells defined by different onesof the base stations. Continued communications with the mobile stationis provided through communication hand off procedures between successiveones of the base stations defining the successive ones of the cellsthrough which the mobile station passes. Through appropriate positioningof the base stations, the mobile station, wherever positioned within thearea encompassed by the communication system, shall be withincommunication proximity of at least one base station.

Only relatively low-powered signals need to be generated to effectuatecommunications between a mobile station and a base station when the basestations are suitably positioned at selected spaced-apart locations.Hand-offs of communications between the successive base stations permitcontinued communications without necessitating increases in the powerlevels at which the communication signals are transmitted. And, becausethe signals that are generated are all generally of low powered levels,the same radio channels are able to be reused at different locations ofthe cellular communication system. The frequency spectrum allocated to acellular communication system is thereby efficiently utilized.

A cellular communication system is constructed, generally, to beoperable pursuant to an operating specification of a particularcommunication standard. Successive generations of communicationstandards have been developed, and operating specifications definingtheir operational parameters have been promulgated. First-generation andsecond-generation cellular communication systems have been deployed andhave achieved significant levels of usage. Third-generation andsuccessor-generation systems are undergoing development,standardization, and, at least with respect to the third-generationsystems, partial deployment.

An exemplary third-generation cellular communication system is a systemthat operates pursuant to the operating protocol set forth in a CDMA2000 operating specification. A CDMA 2000 cellular communication system,constructed in conformity with the CDMA 2000 operating specification,provides for packet-based data communication services.

Various technology proposals by which to effectuate communication ofpacket data at high data rates in a CDMA 2000 communication system havebeen proposed. By transmitting data at high data rates, increasedamounts of data are able to be communicated in a given time period.

The 1×EV-DV data communication service is one such proposal. And, the1×EV-DO data communication service is another such proposal. These datacommunication services provide for the communication of data at any ofseveral selected data rates. And, systems providing for suchcommunication services are sometimes referred to as being multi ratecommunication systems. Other communication systems that permit data tobe communicated at any of two or more different data rates are alsosometimes referred to as being multi rate, or multiple, data ratesystems.

In the CDMA 2000 system that provides for multiple data ratecommunication services, data that is to be communicated is communicatedat selected data rates on reverse links. That is to say, data that iscommunicated by a mobile station to a network portion of thecommunication system is communicated, upon a reverse link channel at aselected data rate. A pilot signal is also communicated by the mobilestation to the network infrastructure along with the communication ofthe data. The pilot signal is communicated upon a reverse pilot channel,and the data is communicated upon a data channel. The pilot signal isused at the network infrastructure to assist in coherent demodulation ofthe data communicated upon the data channel.

In conventional CDMA 2000 systems, i.e., CDMA communication systems thatdo not provide for high data rate communications at multiple data ratesthat are quickly changeable, the pilot signal is of a constant, orslowly changing, signal-to-noise ratio (SNR) level (e.g., received pilotsignal to noise ratio). However, when employed in a system that providesfor multiple data rate communications, such as 1×EV-DV communicationservices, fast scheduling and rate control impact the power controloperation of the communication system. Conventionally, the SNR level ofthe pilot signal must be set at a high SNR level to ensure successfulcommunication of the data at a highest data rate of the multiple datarates. In the event that data is communicated at a data rate that islower than the highest data rate, the pilot signal is of a SNR levelthat is greater than that which is needed. The pilot signal, during suchtimes, therefore, is of an excessive power level. Communicationperformance in the communication system is adversely affected. And, whenthe mobile station is powered by a battery power supply, the batterypower supply is depleted of stored energy at a rate greater than thatwhich is required.

If a better manner could be provided by which better to match the powerlevel of the pilot signal with the data rate at which the dataassociated therewith is communicated, improved system performance wouldbe possible.

It is in light of this background information related to radiocommunication systems capable of communicating data at multiple datarates that the significant improvements of the present invention haveevolved.

SUMMARY OF THE INVENTION

The present invention, accordingly, advantageously provides apparatus,and an associated method, by which to facilitate communications in aradio communication system that provides for data communications atmultiple data rates.

Through operation of an embodiment of the present invention, a pilot, orother control, signal is provided that is of levels related to the datarates at which the data is communicated. When the data rate at whichdata is communicated is changed, the levels at which the pilot, or othercontrol, signal is generated correspondingly changes.

That is to say, through operation of an embodiment of the presentinvention, the pilot, or other control, signal is of a level that ismatched with the data rate at which the data is communicated. The needotherwise to select a highest power level corresponding to a highestdata rate to ensure successful communication of the data is obviated.Operation is permitted, thereby, at reduced power levels. And, lessenedamounts of power are consumed during communication operations, andimproved system performance and increased system capacity are permitted.

When implemented in a CDMA 2000, cellular communication system thatprovides for multiple data rates of data communications, such as thedate rates available in an 1×EV-DV communication service, extra pilotpower on the reverse link is provided. The existing operatingspecification defines, on the reverse link, extending from a mobilestation to the network infrastructure of the communication system, botha reverse fundamental channel and a reverse supplemental channel. Thereverse supplemental channel is provided in significant part, for thecommunication of data pursuant to a 1×EV-DV communication service.

A reverse pilot channel is also defined. The pilot signal is sent by themobile station on the reverse pilot channel along with data on thereverse fundamental channel.

Pursuant to operation of an embodiment of the present invention, areverse supplemental pilot channel is also defined. And, the mobilestation additionally, selectably, sends a supplemental pilot signalthereon. The data communicated upon the reverse fundamental channel is,for instance, of constant, or varying among a set of predefined low,data rates. The pilot signal sent on the reverse pilot channel isselected to be of a level, preferably the smallest possible level, topermit coherent demodulation of the data communicated upon the reversefundamental channel. The pilot signal on the reverse supplemental pilotchannel is of a power level selected responsive to the data rate atwhich the data is sent upon the reverse supplemental channel. When thedata rate of the data communicated upon the reverse supplemental channelis high, the power level of the supplemental pilot signal sent on thereverse supplemental pilot channel is correspondingly high. And, whenthe data rate of the data communicated upon the supplemental channel islow, the power level at which the reverse supplemental pilot signal issent is correspondingly low. By reducing the power level of thesupplemental pilot signal when the data rate of the associated data islow, the power levels of the pilot signals are matched with the datarates of the data that is communicated. And, thereby, transmission ofthe pilot signals at power levels exceeding those that are neededcoherently to demodulate the data communicated upon the reversefundamental and supplemental channels does not occur. Battery powerconsumption at the mobile station is not unnecessarily consumed, andsignal energy on the radio air interface extending between the mobilestation and the network infrastructure is not unnecessarily high.

In one implementation, the pilot power level of the pilot signal sent onthe reverse pilot channel is always of a level needed for the operationof the reverse fundamental channel. That is to say, the T/P ratio of thereverse fundamental channel is independent of the rate in the reversesupplemental channel. That extra pilot power needed for operation of thereverse supplemental channel is provided by the supplemental pilotsignal sent upon the reverse supplemental pilot channel. Fast powercontrol is performed at the network infrastructure, responsive to eitherthe pilot signal sent upon the reverse pilot channel alone, orresponsive to the pilot signals communicated upon both of the reversepilot channel and the reverse supplemental pilot channel.

In another implementation, the mobile station always sets the powerlevel of the pilot signal sent upon the reverse pilot channel. Thereby,the T/P ratio of the data sent upon the reverse fundamental channel isset according to the reverse supplemental channel data rate of a priorframe of data, i.e., data sent during a preceding time period. As thenetwork infrastructure is aware of the data rate of the datacommunicated during a prior time period, the network infrastructure isalso aware of the current T/P ratio upon the reverse fundamentalchannel. And, the network infrastructure adjusts the outer loop powercontrol set point responsive thereto. If the reverse supplementalchannel requires additional pilot power, in addition to the pilot powerprovided upon the reverse pilot channel, then the reverse supplementalpilot signal sent upon the reverse supplemental channel is used toprovide, and obtain, the additional power that is needed.

Pursuant to an additional embodiment of the present invention, a manneris provided by which to facilitate stabling power control in the eventof a data rate change of communication of data during operation of thecommunication system. In one implementation, the adjustment of the pilotreference level is delayed. In another implementation, conservativepower level setting during rate and power control transition isprovided. And, in another implementation, fast rate indications areprovided.

In these and other aspects, therefore, apparatus, and an associatedmethod, is provided for a radio communication system. The radiocommunication system provides for the communication of data by a firstcommunication station on at least a first data channel, at least at afirst selected data rate. A first control signal is communicated upon afirst control channel in which the first control signal is targeted at afirst trigger level during at least a first selected time period.Communication of the data on the at least the first data channel isfacilitated. A second control signal generator selectably generates asecond control signal for communication upon a second control channel.The second control signal is targeted at a second target level. Thesecond target level is selected responsive to the at least the firstselected data rate at which the data is communicated on the at least thefirst data channel.

A more complete appreciation of the present invention and the scopethereof can be obtained from the accompanying drawings, which arebriefly summarized below, the following detailed description of thepresently-preferred embodiments of the invention, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block diagram of a radio communicationsystem operable pursuant to an embodiment of the present invention.

FIG. 2 illustrates a representation of the relationship between the datarates of data communicated upon reverse fundamental and supplementalchannels and the power levels of pilot signals sent on reverse pilot andreverse supplemental pilot channels during operation of an embodiment ofthe present invention.

FIG. 3 illustrates a representation, similar to that shown in FIG. 2,also representative of the relationship between data rates at which datais communicated on reverse link channels and power levels of pilotsignals generated on reverse pilot and supplemental pilot channels,here, pursuant to operation of another embodiment of the presentinvention.

FIG. 4 illustrates a representation of an exemplary power controlsubchannel structure of the reverse pilot and supplemental pilotchannels defined pursuant to an embodiment of the present invention.

FIG. 5 illustrates a representation, similar to those shown in FIGS.2-3, here showing the relationship between the data rates at which datais communicated upon the reverse supplemental channel and the powerlevel of a pilot signal generated upon a reverse pilot channel pursuantto operation of an embodiment of the present invention.

FIG. 6 illustrates a timing diagram representing the timing relationshipof rate request and grant scheduling pursuant to operation of anembodiment of the present invention.

FIG. 7 illustrates a representation of the generation of rateindications on a reverse pilot channel generated pursuant to operationof an embodiment of the present invention.

DETAILED DESCRIPTION

Referring first to FIG. 1, a radio communication system, shown generallyat 10, provides for radio communications, in a multi-user environment,with mobile stations, of which the mobile station 12 is representative.The communication system forms a multiple data rate communication systemin which data is communicated, selectably at a selected data rate of aplurality of separate, allowable data rates. In the exemplaryimplementation, the communication system forms a CDMA 2000 cellularcommunication system that provides for 1×EV-DV communication services.That is to say, in the exemplary implementation, the communicationsystem is compliant, generally, with the operating protocols set forthin the CDMA 2000/1×EV-DV operating specification.

The teachings of the present invention, are, however, amenable for usein other types of multi rate data communication systems. While thefollowing description of operation of various embodiments of the presentinvention shall be described with respect to their implementation in aCDMA 2000 cellular communication system that provides for 1×EV-DV datacommunications, the teachings of the present invention are analogouslyapplicable to other types of communication systems.

Two-way communication of data between a mobile station and a networkpart of the communication system is provided. A radio air interface isdefined between the network part of the communication system and mobilestations operable therein. Forward link channels are defined uponforward links extending from the network part to the mobile stations.And, reverse link channels are defined upon reverse links extending fromthe mobile stations to the network part of the communication system.Both control information and data traffic is communicated between thenetwork part and the mobile stations upon the forward and reverse linkchannels.

The operating specification pursuant to which the communication systemis constructed to be in compliance defines various control and datachannels upon the forward and reverse links. Of significance to anembodiment of the present invention, in the exemplary implementation, areverse fundamental channel (R-FCH) and a reverse supplemental channel(R-SCH) are defined upon which to communicate, from a mobile station tothe network part, traffic data, communicated pursuant to effectuation ofa data communication service. The arrow 14 represents the reversefundamental channel upon which data is communicated by the mobilestation 12 to the network part of the communication system, and thearrow 16 is representative of a reverse supplemental channel upon whichtraffic data is also communicated by the mobile station to the networkpart. More particularly, the reverse supplemental channel is generallyutilized upon which to communicate 1×EV-DV data at any of variousselected data rates. The data rates at which the data is communicatedupon the reverse supplemental channel is susceptible to abrupt changes.

Various control channels are also defined on the reverse link. Includedamongst the control channels is a reverse pilot channel (R-PICH),represented by the arrow 22. Pursuant to an embodiment of the presentinvention, an additional channel, a reverse supplemental pilot channel(R-SPICH) is defined. The reverse supplemental pilot channel isrepresented in the Figure by the arrow 22. And, forward link channels,both traffic and control channels, are represented in the Figure by thearrow 28.

The network infrastructure of the communication system is here shown toinclude a base station 34. The base station includes transceivercircuitry for transceiving data upon the forward and reverse linkchannels defined upon the radio air interface extending between thenetwork part and the mobile stations of the communication system. In theexemplary implementation, the base station operates pursuant to a CDMA(code-division, multiple-access) communication scheme. The base stationfurther includes circuitry and elements to perform various functions,such as power control functions that power control of signals generatedduring operation of the communication system.

The base station 34 forms a portion of a radio access network portion ofthe network part of the communication system. The radio access networkalso includes a base station controller (BSC) 36 to which the basestation 34 is coupled. The base station controller operates, amongstother things to control operation of the base station 34, as well asother base stations to which the base station controller is coupled. Theradio access network is here shown to be coupled to a packet datanetwork (PDN) 38, here by way of a gateway (GWY) 40. A correspondentnode (CN) 42 is coupled to the packet data network. The correspondentnode is representative of a communication node that forms an ultimatesource, or ultimate destination, of data communicated with the mobilestation 12. A computer station, a telephonic station, and a contentserver are all exemplary of devices of which the correspondent node canbe comprised.

Various elements of the base station 34 are also represented in FIG. 1.Here, the front end transmit and front end receive circuit portions 48and 52, respectively, are shown. The front end transmit and receiveportions perform functions such as up-conversion and down-conversion,respectively, operations upon data that is communicated upon the radioair interface. The front end receive circuitry portion is coupled to adecoder and to a signal-to-noise ratio (SNR) estimator 56. And, thedecoder is coupled to a frame error rate (FER) estimator 58. Theestimators 56 and 58 operate upon indications of data received by thefront end receive circuitry to generate estimates of signal to noiseratios and frame error rates of the indications provided thereto. Valuesrepresentative of the estimate generated by the estimator 56 on the line62 are provided to a comparator 66. And, values representative of theestimates generated by the estimator 58 on the line 67 are provided toan outer loop power control element 74. The elements 66 and 74 formportions of the transmit chain of the base station. A value of a targetframe error rate (TG FER) 75 is also provided to the outer loop powercontrol element 74. The outer loop power control element forms a valuethat is applied to the comparator 66, and a comparator output isprovided to the front transmit circuitry 48. Power control iseffectuated through the communication of, inter alia., power controlcommands that instruct the mobile station as to at what power levels atwhich to communicate data on the reverse data channel (R-FCH).

As mentioned previously, pilot signals are communicated by the mobilestation to facilitate coherent demodulation of the data communicatedupon the reverse data channels. The pilot signal is of an adequate powerlevel to permit the informational content of the data communicated bythe mobile station to the network infrastructure adequately to berecovered. Because of the direct relationship between the power level atwhich the pilot signal must be sent and the data rate at which thetraffic data is sent, and its effect upon power control, conventionallythe power level at which the pilot signal is sent is set to be of apower level corresponding to the power level required of the pilotsignal associated with data communicated at a highest possible datarate. When data is communicated at a data rate less than the highestpossible data rate, the power level of the pilot signal is unnecessary.

An embodiment of the present invention comprises apparatus, showngenerally at 82, embodied at mobile stations, such as the mobile station12. The apparatus includes a second pilot, or other control, signalgenerator 84. The signal generator generates a pilot signal of a powerlevel responsive to the data rate at which data is communicated by themobile station upon the reverse supplemental channel. In oneimplementation, the pilot signal is unmodulated. In otherimplementations, the pilot signal is modulated by a known sequence, by apseudodeterminative sequence, or by other values. The indication of thedata rate at which the data is communicated by the mobile station uponreverse supplemental channel is provided to the second pilot signalgenerator by way of the line 86. The indication is here represented tobe provided by a data source that forms part of the transmit chain,together with the transmit circuitry of the mobile station. And, thesignal formed, or caused to be formed, by the second control signalgenerator is communicated by the transmit circuitry of the mobilestation. As the data rate changes, the power level of the additionalpilot signal formed by the signal generator 84 correspondingly changes,thereby matching the power level of the signal with the data rate of thetraffic data that is communicated.

FIG. 2 illustrates a representation of exemplary data rates of datacommunicated upon the reverse fundamental channel 14 and the reversesupplemental channel 16 during successive time frames or other timeperiods. And, corresponding power levels at which pilot signals are sentupon the reverse pilot channel 22 and reverse supplemental pilot channel24 pursuant to operation of an embodiment of the present invention arealso represented. In this implementation, the power level of the pilotsignal sent by the mobile station upon the reverse pilot channel 24 isof a pilot power level needed for operation of the reverse fundamentalchannel. That is to say, the T/P ratio of the reverse fundamentalchannel is independent of the rate of the reverse supplemental channel.The additional pilot power that is needed for operation of the reversesupplemental channel 16 is provided by the supplemental pilot signalsent on the reverse supplemental pilot channel 24. When detected at thebase station, fast power control is performed based upon pilot signalssent on the reverse pilot channel only, or upon both the reverse pilotchannel and the supplemental pilot signal sent upon the reversesupplemental pilot channel.

In the event of variable rate operation, i.e., when the data rate atwhich the data is communicated on the supplemental channel changes, thepilot signal sent upon the reverse pilot channel is transmitted at alowest possible power level that can ensure the performance of thecommunication of the data on the reverse fundamental channel. The powerlevel of the supplemental pilot signal sent upon the reversesupplemental channel is set to be:P=(10^(pilot) ^(_) ^(reference) ^(_) ^(level*0.125/10)−1.0)*R-PICH.

If the T/P ratio of the reverse supplemental channel is defined to bethe ratio of the power of the reverse supplemental channel to the powerof the combination of the reverse pilot channel and the reversesupplemental pilot channel, then the T/P ratio of the reversesupplemental channel is set to a value of a nominal attribute gain ofthe rate that is currently used. Power is not wasted. And, as the T/Pratio of the reverse fundamental channel is independent of the rate ofthe reverse supplemental channel, the power control loop is notdisturbed by the data rate change in the reverse supplemental channel.

FIG. 3 illustrates again the relationships between the data rates of thedata communicated upon the reverse fundamental and supplemental channels14 and 16 and the power levels of the pilot signals upon reverse pilotchannel and reverse supplemental pilot channel 22 and 24 duringsuccessive time frames. In this implementation, the power level of thepilot signal sent by the mobile station sent on the reverse pilotchannel is set by the mobile station. And, hence, the T/P ratio of thereverse fundamental channel, all according to the data rate of the datacommunicated upon the reverse supplemental channel in a previous frame.As the base station knows also the data rate of the data communicatedupon the reverse supplemental channel during the prior time frame, thebase station also knows of the current T/P ratio of the datacommunicated upon the reverse fundamental channel and adjusts the outerloop power control set point accordingly. If the current reversesupplemental channel requires additional pilot power than provided onthe reverse pilot channel during the current time frame, the reversesupplemental pilot channel is used to communicate a supplemental pilotsignal to provide the extra power.

In this implementation, the power control loop is not independent of thedata rate change of the reverse supplemental channel. But, the powercontrol loop is relatively undisturbed by the rate change in that thebase station is aware of how to adjust the outer loop power control setpoint at each frame boundary. In this scheme, an improved SNR estimateis provided for use upon inner loop power control as the pilot signalsent on the reverse pilot channel is generally of a relatively highpower. Hence, the power control made possible in this implementation isfairly accurate.

FIG. 4 illustrates a representation, shown generally at 102, ofexemplary power control subchannel structures of the reverse pilotchannel 22 and the reverse supplemental pilot channel 24. Asillustrated, the reverse pilot channel is formed of a first portion 104of a length of 1152 chips and a 384 chip-length reverse power controlsubchannel 106. Similarly, the reverse supplemental pilot channel 24 isalso formatted to include a first portion 108 of a 1152 chip length anda 384 chip length portion 112 forming the reverse pilot controlsubchannel values. A code, for example, W₃₂ ⁶⁴ can be assigned to thereverse supplemental pilot channel. Backward compatibility is preservedthrough use of this type of structure.

FIG. 5 illustrates a representation of the relationship between the datarates at which communication data is communicated upon the reversefundamental and supplemental channels 14 and 16 and the power level ofthe pilot signal sent upon the reverse pilot channel. In thisimplementation, the reference level of the pilot signal is delayedfollowing a data rate change of the communication data, communicatedupon the data channels. At time 106, the outer loop power control setpoint is as indicated by the opposing arrows. This is the power controlset point prior to a rate change of data communicated upon the reversesupplemental channel. At time 108, the data rate of the datacommunicated upon the reverse supplemental channel increases. Time 110defines the start of a subsequent time frame. And, thereafter, during asubsequent time frame, the pilot power and outer loop set point isadjusted. During this subsequent time period, the quality of the reversefundamental channel and the reverse supplemental channel is maintained.At time 112, the data rate of the data communicated upon the reversesupplemental channel again changes. And, subsequent to time 114, thepilot power is again adjusted. And, as indicated at the time 116, theouter loop set point is again indicated by the opposing arrows.

During the first frame following the data rate change at the time 108, asequence of procedures is performed at the mobile station. The T/P ratioof the reverse fundamental channel is maintained. And, the T/P ratio ofthe reverse supplemental channel is adjusted according to the nominalattribute gain of the new data rate plus the difference between thepilot reference level and the new data rate and the old data rate.During this frame, the power level of the reverse supplemental channelis set according to the new rate, but the target received SNR of thereverse pilot channel and reverse fundamental channel are maintained atthe same level as in the prior frame. And, at the base station, as thebase station is unaware of the rate change of the data communicated uponthe reverse supplemental channel, the base station power control actionscontinue as is no rate change has occurred.

During the second time frames, commencing at the time 110, following thedata rate change, the mobile station adjusts the power level of thepilot signal by the difference between the pilot reference level of thenew data rate and the old data rate. Additionally, the T/P ratio of thereverse supplemental channel is adjusted according to the nominalattribute gain of the new data rate. And, the T/P ratio of the reversefundamental channel is adjusted according to the multiple channel gainof the new data rate. At the base station, the rate indicator in thefirst frame following the data rate change is received. The base stationthereby has knowledge of the new data rate. And, the base stationadjusts the outer loop power control threshold to the initial targetouter loop power control threshold of the new data rate.

FIG. 6 illustrates rate requests 118, rate grants 122, and reversesupplemental channel values 124 during operation of an embodiment of thepresent invention. In this implementation, data rate changes and powerlevel adjustments, and adjustments to the T/P ratios are made accordingto the nominal attribute gain and multiple channel adjustment gains, allas specified in the operating specification of CDMA 2000. Without theknowledge of the current rate, the base station assumes the mobilestation to transmit at a highest rate allowed by the previous rategrant. And, the outer loop power control threshold is set accordingly.

In the exemplary operations set forth in FIG. 6, the rate of the datacommunicated upon the reverse supplemental channel is always equal to orless than, the data rate that is granted by the base station. That is tosay, Rate_I is less than or equal to Rate_grant_I. Because the basestation does not know the data rate of the data communicated upon thereverse supplemental channel until the rate indicator is receivedcorrectly, the base station assumes the current rate, Rate_I equals theRate_grant_i. And, the outer loop power control threshold is setaccordingly. Through this operation, there is always enough power in thepilot signal sent on the reverse pilot channel to guarantee the requiredframe error rate on the reverse supplemental channel.

FIG. 7 illustrates an implementation in which a fast rate indication ismultiplexed into the reverse pilot channel, thereby to provide the basestation with an indication of the data rate change at the earliestpossible time. The first sequence 126, illustrates the reverse pilotchannel and the reverse power control subchannel during successive timeperiods within a time frame, each defining a power control group 128.

The second sequence illustrates the reverse pilot and reverse pilotchannel and reverse power control subchannel together with a reversefast rate indication subchannel (R-FRISCH) 132 defined pursuant to anembodiment of the present invention. And, the third sequence illustratesthe reverse pilot channel, the reverse fast rate indication subchanneland reverse power control subchannel defined pursuant to operation ofanother embodiment of the present invention.

As the Figure illustrates, selected power control bits, such as thefirst one or two power control bits of the reverse link power controlsubchannel are punctured with values that define the reverse fast rateindication subchannel. In one implementation, a pilot signal generator,such as the pilot signal generator 84 shown in FIG. 1 also operates as arate indication generator that generates rate indications that indicatethe data rate that is inserted into the illustrated positions. Inanother implementation, the values are inserted even earlier.Alternately, the mobile station can also puncture a portion of thereverse pilot channel in the first and second power control group. Therate indication bits inserted into these positions form this subchannel,the R-FRISCH. The mobile station changes data rates and adjusts thepower levels and T/P ratios according to the nominal attribute gain andmultiple channel adjustment gain, all as specified in the operatingspecification of the CDMA 2000 system. The base station holds the outerloop power control thresholds in the first one or two power controlgroups of this frame, and adjusts the outer loop power control thresholdthereafter according to the rate change information conveyed in thereverse fast rate indication subchannel. Fast rate indication canalternately be realized in other manners, such as by multiplexing thevalues together with the reverse rate indicator channel (R-RICH). Thedefinition and use of the R-FRISCH permits a base station to adjust theouter loop power control threshold quickly. The bits can also be usedtogether with the R-RICH to decode the detail rate indicationinformation in a finer resolution.

Through operation of any of these embodiments of the present invention,fast stabling of the power control loop is provided with minimal changeto the existing operating specification.

The preferred descriptions are of preferred examples for implementingthe invention, and the scope of the invention should not necessarily belimited by this description. The scope of the present invention isdefined by the following claims.

We claim:
 1. A method comprising: receiving a pilot signal on a reversepilot channel and a supplemental pilot signal on a reverse supplementalpilot channel; receiving data on a reverse data channel, wherein a powerlevel of the received supplemental pilot signal varies based onvariations in a data rate on the reverse data channel; and demodulatingthe reverse data channel in a coherent manner based on the pilot signaland the supplemental pilot signal.
 2. The method of claim 1, furthercomprising performing outer loop power control based upon the reversepilot channel and the reverse supplemental pilot channel.
 3. The methodof claim 2, wherein the reverse pilot channel and the reversesupplemental pilot channel each include a reverse power controlsubchannel.
 4. The method of claim 3, wherein the reverse power controlsubchannel in the reverse pilot channel includes a reverse fast rateindicator providing an indication of the data rate on the reverse datachannel, wherein the performing of outer loop power control is based onthe reverse fast rate indicator.
 5. The method of claim 4, furthercomprising: during a first time frame, maintaining outer loop powercontrol thresholds; and during a second time frame following the firsttime frame, adjusting the outer loop power control thresholds based onthe indication of the data rate on the reverse data channel provided inthe reverse fast rate indicator.
 6. The method of claim 5, wherein thevariations in the data rate occurred during the first time frame.
 7. Themethod of claim 1, further comprising: performing outer loop powercontrol based upon a traffic-to-pilot ratio of the reverse data channel.8. The method of claim 1, wherein the power level of the receivedsupplemental pilot signal is generated in response to the data rate onthe reverse data channel exceeding a predetermined target level datarate.
 9. The method of claim 8, wherein the pilot signal has a constantpower level.
 10. An apparatus comprising: a receiver circuit configuredto receive a reverse pilot channel including a pilot signal, a reversesupplemental pilot channel including a supplemental pilot signal, anddata on a reverse data channel including modulated data, wherein a powerlevel of the supplemental pilot signal is adjusted based on variationsin a data rate on the reverse data channel; and a demodulator configuredto demodulate the data on the reverse data channel in a coherent mannerbased on the pilot signal and the supplemental pilot signal.
 11. Theapparatus of claim 10, further comprising power control circuitryconfigured to perform outer loop power control based upon the reversepilot channel and the reverse supplemental pilot channel.
 12. Theapparatus of claim 11, wherein the reverse pilot channel and the reversesupplemental pilot channel each include a reverse power controlsubchannel.
 13. The apparatus of claim 12, wherein the reverse powercontrol subchannel in the reverse pilot channel includes a reverse fastrate indicator providing an indication of the data rate on the reversedata channel, wherein the power control circuitry is configured toperform the outer loop power control based on the reverse fast rateindicator.
 14. The apparatus of claim 13, wherein the power controlcircuity is configured to, during a first time frame, maintain outerloop power control thresholds and, during a second time frame followingthe first time frame, adjust the outer loop power control thresholdsbased on the indication of the data rate on the reverse data channelprovided in the reverse fast rate indicator.
 15. The apparatus of claim14, wherein the variations in the data rate occurred during the firsttime frame.
 16. The apparatus of claim 10, further comprising powercontrol circuitry configured to perform outer loop power control basedupon a traffic-to-pilot ratio of the reverse data channel.
 17. Theapparatus of claim 10, wherein the power level of the supplemental pilotsignal is generated in response to the data rate on the reverse datachannel exceeding a predetermined target level data rate.
 18. Theapparatus of claim 17, wherein the pilot signal has a constant powerlevel.